Autotrophic CO2 fixation in Chlorobium limicola. Evidence for the operation of a reductive tricarboxylic acid cycle in growing cells

1980 ◽  
Vol 128 (1) ◽  
pp. 64-71 ◽  
Author(s):  
Georg Fuchs ◽  
Erhard Stupperich ◽  
Gerolf Eden
Keyword(s):  
Co2 Fixation ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Chlorobium Limicola ◽  
Autotrophic Co2 Fixation ◽  
Acid Cycle ◽  
Reductive Tricarboxylic Acid Cycle

Structure, Carbon Dioxide Fixation and Metabolism of Stomata

1974 ◽  
Vol 1 (2) ◽  
pp. 221 ◽  
Author(s):  
CJ Pearson ◽  
FL Milthorpe
Keyword(s):  
Carbon Dioxide ◽  
Organic Acid ◽  
Co2 Fixation ◽  
Tricarboxylic Acid Cycle ◽  
Guard Cells ◽  
Tricarboxylic Acid ◽  
Light Illumination ◽  
Acid Cycle ◽  
Free Air ◽  
Positive Correlations

Studies were made of the structure and rates of CO2 fixation of epidermis and of changes in organic metabolites in Commelina cyanea during transition to light and dark in both normal and CO2-free air. Guard cells of C. cyanea and Vicia faba contain numerous highly developed mitochondria and starch-forming chloroplasts (mitochondria: chloroplast ratios of 3 : 1) in comparison to other epidermal cells with few mitochondria and rudimentary plastids without starch. Their rates of photosynthesis per chloroplast appeared to be at least as high as those of the mesophyll, but circumstantial evidence suggested that about half of current photosynthate was respired. The rate of CO2 fixation in the dark was about 0.2–0.4% of that in the light. Illumination caused an increase, and darkening a decrease, of aperture, malate, and organic acid 1% within the epidermis of C. cyanea. Darkening in CO2-free air was accompanied by only slight decreases in aperture and malate. There were close positive correlations between aperture and concentration of malate and between aperture and organic acid 14C. During opening, the rise in organic acid 14C was associated with a decline in amino acid 14C. It is suggested that organic acids may be formed through aspartate and possibly also from sugars and other amino acids entering the tricarboxylic acid cycle. Concentrations of sugars were not related to aperture although they increased on illumination and declined about 2 h after darkening. Polysaccharide concentrations in the epidermis of darkened leaves were similar to those in illuminated leaves.

scholarly journals A Soluble NADH-Dependent Fumarate Reductase in the Reductive Tricarboxylic Acid Cycle of Hydrogenobacter thermophilus TK-6

2008 ◽  
Vol 190 (21) ◽  
pp. 7170-7177 ◽  
Author(s):  
Akane Miura ◽  
Masafumi Kameya ◽  
Hiroyuki Arai ◽  
Masaharu Ishii ◽  
Yasuo Igarashi
Keyword(s):  
Soluble Fraction ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Fumarate Reductase ◽  
High Sequence Identity ◽  
Catalytic Subunits ◽  
Acid Cycle ◽  
Genes Encoding ◽  
Hydrogenobacter Thermophilus ◽  
Reductive Tricarboxylic Acid Cycle

ABSTRACT Fumarate reductase (FRD) is an enzyme that reduces fumarate to succinate. In many organisms, it is bound to the membrane and uses electron donors such as quinol. In this study, an FRD from a thermophilic chemolithoautotrophic bacterium, Hydrogenobacter thermophilus TK-6, was purified and characterized. FRD activity using NADH as an electron donor was not detected in the membrane fraction but was found in the soluble fraction. The purified enzyme was demonstrated to be a novel type of FRD, consisting of five subunits. One subunit showed high sequence identity to the catalytic subunits of known FRDs. Although the genes of typical FRDs are assembled in a cluster, the five genes encoding the H. thermophilus FRD were distant from each other in the genome. Furthermore, phylogenetic analysis showed that the H. thermophilus FRD was located in a distinct position from those of known soluble FRDs. This is the first report of a soluble NADH-dependent FRD in Bacteria and of the purification of a FRD that operates in the reductive tricarboxylic acid cycle.

scholarly journals Elimination and replenishment of tricarboxylic acid-cycle intermediates in myocardium

1981 ◽  
Vol 194 (3) ◽  
pp. 867-875 ◽  
Author(s):  
E M Nuutinen ◽  
K J Peuhkurinen ◽  
E P Pietiläinen ◽  
J K Hiltunen ◽  
I E Hassinen
Keyword(s):  
Co2 Fixation ◽  
Tricarboxylic Acid Cycle ◽  
Linear Optimization ◽  
Tricarboxylic Acid ◽  
Acid Cycle ◽  
Rat Hearts ◽  
Label Incorporation ◽  
Perfused Rat Hearts ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Isolated Perfused Rat Hearts

1. The contribution of Co2 fixation to the anaplerotic mechanisms in the myocardium was investigated in isolated perfused rat hearts. 2. K+-induced arrest of the heart was used to elicit a transition in the concentrations of the intermediates of the tricarboxylic acid cycle. 3. Incorporation of 14C from [14]bicarbonate into tricarboxylic acid-cycle intermediates was measured and the rates of the reactions of the cycle were estimated by means of a linear optimization program which solves the differential equations describing a simulation model of the tricarboxylic acid cycle and related reactions. 4. The results showed that the rate of CO2 fixation is dependent on the metabolic state of the myocardium. Upon a sudden diminution of cellular ATP consumption, the pool size of the tricarboxylic acid-cycle metabolites increased and the rate of label incorporation from [14C]bicarbonate into the cycle metabolites increased simultaneously. The computer model was necessary to separate the rapid equilibration between bicarbonate and some metabolites from the potentially anaplerotic reactions. The main route of anaplerosis during metabolite accumulation was through malate + oxaloacetate. Under steady-state conditions there was a constant net outward flow from the tricarboxylic acid cycle via the malate + oxaloacetate pool, with a concomitant anaplerotic flow from metabolites forming succinyl-CoA (3-carboxypropionyl-CoA).

scholarly journals Systems-informed genome mining for electroautotrophic microbial production

2020 ◽  
Author(s):  
Anthony J. Abel ◽  
Jacob M. Hilzinger ◽  
Adam P. Arkin ◽  
Douglas S. Clark
Keyword(s):  
Carbon Fixation ◽  
Microbial Respiration ◽  
Tricarboxylic Acid Cycle ◽  
Genome Mining ◽  
Tricarboxylic Acid ◽  
Nitrate Respiration ◽  
Fixation Rate ◽  
Acid Cycle ◽  
Carbon Molecules ◽  
Reductive Tricarboxylic Acid Cycle

AbstractMicrobial electrosynthesis (MES) systems can store renewable energy and CO2 in many-carbon molecules inaccessible to abiotic electrochemistry. Here, we develop a multiphysics model to investigate the fundamental and practical limits of MES enabled by direct electron uptake and we identify organisms in which this biotechnological CO2-fixation strategy can be realized. Systematic model comparisons of microbial respiration and carbon fixation strategies revealed that, under aerobic conditions, the CO2 fixation rate is limited to <6 μmol/cm2/hr by O2 mass transport despite efficient electron utilization. In contrast, anaerobic nitrate respiration enables CO2 fixation rates >50 μmol/cm2/hr for microbes using the reductive tricarboxylic acid cycle. Phylogenetic analysis, validated by recapitulating experimental demonstrations of electroautotrophy, uncovered multiple probable electroautotrophic organisms and a significant number of genetically tractable strains that require heterologous expression of <5 proteins to gain electroautotrophic function. The model and analysis presented here will guide microbial engineering and reactor design for practical MES systems.

Inhibition of CO2 fixation in group D streptococci

1969 ◽  
Vol 15 (1) ◽  
pp. 57-60 ◽  
Author(s):  
Victor F. Lachica ◽  
Paul A. Hartman
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Pyruvate Carboxylase ◽  
Co2 Fixation ◽  
Tricarboxylic Acid Cycle ◽  
Inhibitory Effect ◽  
Tricarboxylic Acid ◽  
Acetyl Coa ◽  
Acid Cycle ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Group D

The stimulatory effect of acetyl-CoA and the inhibitory effect by L-aspartate and some intermediates of the tricarboxylic acid cycle in the assimilation of CO2 by crude extracts of group D streptococci suggest that the pyruvate carboxylase of Streptococcus faecium and the phosphoenolpyruvate carboxylase of S. bovis are allosteric enzymes. This implies that these enzymes are sites for the control of the amount of aspartate and of the tricarboxylic acid cycle intermediates synthesized.

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